How to model an irregular object made of tubes?
Objects that are made out of tubes can be modelled with curve objects.


Shift+A> Curve> Bezier
On the curve properties make the curve fill type 'full' and set the Bevel depth and resolution to increase the diameter of the tube and the smoothness of it:




The curve on the left is what it looks like after adding it and editing it's shape in edit mode. The curve on the right is after the above settings have been applied.



You can extrude this curve and edit it similarly to how you would edit a mesh, using scaling, rotating and moving to manipulate the curve handles.

If at some point you want it to be a mesh you can select the curve and choose Alt+C> Mesh from Curve